Many integrated circuit (“IC”) devices require exposure to a source of light at a point during their operational cycle. Such IC devices can include, for example, EPROMs, CCD imaging chips, and various other chips or IC devices with a light sensing component. In many such IC devices that require some sort of exposure to light, and indeed in most all IC devices, the device must generally be enclosed in a sealed environment to protect it and its associated electrical connections from damage due to exposure to the outside environment. Accordingly, numerous conventional packages for IC devices involve the formation of a window or other transparent component that enables light to reach one or more components on the IC device.
Early IC device packages designed to address this issue have involved the formation of a ceramic base and lid adapted to support the IC device, as well as a transparent window situated near the light sensing component. Later packages to accomplish this light providing function have included a transparent plastic or other material as the actual encapsulant for the IC device. As will be readily understood, the term “translucent” may be used in place of the terms “transparent” or “clear” for many of the items, materials and/or other light specific applications throughout this disclosure. Various references that involve providing light to a packaged IC device or component via a transparent or translucent window or other light passing channel can be found at, for example, U.S. Pat. Nos. 4,663,833; 4,766,095; 4,971,930; 5,034,800 and 7,199,438, as well as Japanese Patent No. 62-174956.
Where a light passage through a package is provided by using transparent material as the encapsulant for an IC device, several problems have arisen. For one thing, an encapsulant made entirely of transparent material can result in a package that allows light to reach places on the IC device where light is not desirable. For another, the production of a transparent compound to use as an encapsulant can be significantly more costly than the production of a typical silica-based encapsulant compound. Often, the cost of a transparent encapsulant compound can be roughly ten times that of a regular encapsulant compound. Another drawback is that transparent encapsulant compounds are typically produced by removing black pigment and silica from a regular encapsulant compound, which results in a clear compound that is less able to withstand stresses and thermal shock effects. As yet another drawback, many transparent encapsulant compounds are not readily marked by laser markings, which is a preferred way to mark the outside of a packaged chip. As such, packages having an entirely transparent encapsulant material are difficult or impossible to laser mark.
While many of the devices and techniques to provide light to an IC device via a packaging feature have generally worked well in the past, there is always a desire to provide more reliable and cost effective ways for packaging such IC devices.